New terpenoids and thiophene derivatives from the aerial parts of Artemisia sieversiana

One new highly oxygenated nortriterpene, named sieverlactone (1), one new sesquiterpene, 1β,10β-epoxy-8α-acetoxyachillin (2), one new natural product, 5-propinyl-thiophene-2-carboxylic acid (3), and one new thiophene, 3-hydroxy-5-propinyl-2-acetyl-thiophene (4), together with 10 other known compounds (5?14), were isolated from the dried aerial parts of Artemisia sieversiana. Their structures were elucidated by a combination of extensive spectroscopic analysis, including 1D, 2D NMR spectroscopic and mass spectrometric data. Meanwhile, the stereochemistry of 1 and 2 was confirmed by single-crystal X-ray diffraction technique using Cu radiation. All the isolates were evaluated for their anti-neuroinflammatory effects on the lipopolysaccharide-induced nitric oxide production in BV-2 murine microglial cells. Compounds 2, 5, and 6 exhibited the significant activities with IC₅₀ values of 6.5?±?0.5, 11.9?±?0.7, and 10.1?±?0.3?μM, respectively, comparable to the positive control, quercetin, with an IC₅₀ value of 16.3?±?0.4?μM.